British study shows genetics to be key factor in students' GCSE exam results
Study of 11,000 British teenagers finds DNA, not home life or quality of schools and teachersbest explains differences in pupils' test scores
The Guardian in London
Differences in children's examination results at secondary school owe more to genetics than teachers, schools or family environment, a British study has found.
The research drew on the exam scores of more than 11,000 16-year-olds who sat Britain's general certificate of secondary education (GCSE) exams.
In English, maths and science, genetics accounted for on average 58 per cent of the differences in scores that children achieved.
Grades in the sciences (such as physics, biology and chemistry) were more heritable than those in humanities subjects (such as art and music), at 58 per cent and 42 per cent respectively.
The findings do not mean that children's performance at school is determined by their genes, or that schools and the child's environment have no influence. The overall effect of a child's environment - including their home and school life - accounted for 36 per cent of the variation seen in exam scores across all subjects, the study found.
"The question we are asking is why do children differ in their GCSE scores? People immediately think it's schools. But if schools accounted for all the variance, then children in one classroom would all be the same," said Robert Plomin, an expert in behavioural genetics who led the study at King's College London.
To tease out the genetic contribution to children's school grades, the researchers studied GCSE scores of identical twins (who share 100 per cent of their genes) and non-identical twins (who share on average half of the genes that normally vary between people). Both groups share their environments to a similar extent.
Comparing the twins' exam scores allowed the scientists to work out how much of the variation was the result of genetics, and how much environment. For example, when identical twins get different GCSE scores, the cause cannot be genetic, so it must be what scientists call "non-shared environment" effects, such as the better student having a better teacher.
A child's performance is influenced, but not set, by their DNA. While one child may excel, their identical twin may not. But taking an average over the population studied, around half of the variation in GCSE scores was due to genetics, Plomin found. Details of the study appear in the journal PLOS One.
Writing in the journal, the authors point out that genetics emerges as such a strong influence on exam scores because the schooling system aims to give all children the same education. The more school and other factors are made equal, the more genetic differences come to the fore in children's performances.
The same situation would happen if everyone had a healthy diet: differences in body weight would be more the result of genetic variation, instead of being dominated by lifestyle.
Plomin said one message was that differences in children's performance were not merely the result of effort.
"Some children find it easier to learn than others, and I think it's appetite as much as aptitude," he said. "There is a motivation, maybe because you like to do what you are good at."
Michael Reiss, professor of science education at the Institute of Education in London, said that while genetics undoubtedly plays a role in educational performance, the information might not be all that useful.